Full-adder notation – are the inputs conventionally labeled A1, B1, and Cin?

Introduction / Context:
Naming conventions in schematics vary, but there are widely used standards. A full adder takes three inputs (two operand bits and a carry-in) and produces Sum and Cout. The canonical labels are A, B, and Cin (or X, Y, Cin). This question checks whether A1 and B1 are the standard required labels.

Given Data / Assumptions:

• Standard full-adder block.
• Common schematic conventions from textbooks and datasheets.
• Subscripts sometimes denote bit positions (e.g., A0, A1), but are not mandatory labels.

Concept / Approach:
The conventional notation is A, B, and Cin. Using A1 and B1 might indicate the bit-1 position in a multi-bit word (e.g., A1, B1, Cin1), but that is a positional index, not the standard naming requirement. Therefore, stating that the inputs are labeled A1, B1, and Cin as a rule is inaccurate.

Step-by-Step Solution:

Verification / Alternative check:
Textbook and HDL descriptions (e.g., Verilog) typically declare modules with ports (A, B, Cin) and index vectors for bit positions, confirming the norm.

Why Other Options Are Wrong:
BCD or carry-save architectures do not change generic labeling practice; indices remain contextual rather than prescriptive.

Common Pitfalls:
Confusing a specific schematic’s indices with universal naming. Always separate functional role names from bit-position subscripts.

Final Answer:
Incorrect